Adult-onset neurodegenerative diseases (NDs) represent a group of diseases including Alzheimer's disease, Parkinson's disease, and various tauopathies, characterized by similar phenotypic manifestations. With an increasingly aging society, these adult-onset NDs represent a significant public health problem. A key barrier to the ND field has been the inability to monitor the cellular basis of neurodegeneration in vivo. In order to develop targeted and effective therapeutics and diagnostics for these devastating disease, it is imperative to understand the mechanisms contributing to early stages and to progression of neurodegenerative diseases in vivo. Increasing evidence has shown a link between aberrant neuronal intracellular trafficking and neurodegeneration, with mouse models of Alzheimer's disease and other tauopathies showing axonal transport defects. However, the relationship between these defects and the end-point of neurodegeneration has not been elucidated. It is possible that aberrantly transported RNAs, proteins, or organelles could lead to altered neuronal function and morphology and eventually to cell death. It is equally possible, however, that the defective transport seen in ND states is a secondary pathology that only develops following other initial insults. These studies using the Zebrafish system will test the hypothesis that disrupted neuronal transport of RNAs, vesicles, and organelles represents an important early event in NDs and that modulating specific motors may alleviate hallmark pathologies of ND. The Zebrafish embryo is optically transparent and genetically accessible, allowing for in vivo imaging of disease models and fundamental features of the nervous system are conserved between Zebrafish and humans. To address this hypothesis, the MS2/MCP RNA-labeling system has been adapted for Zebrafish to facilitate in vivo analysis of neuronal RNA transport. Using transgenic lines that have been generated, a select group of RNAs will be tracked by time-lapse confocal microscopy to monitor the dynamics of axonal transport in vivo. These studies will also be carried out using a Zebrafish tauopathy model to ascertain whether disrupted RNA transport is a prominent feature of NDs. Zebrafish kinesin mutants will then be characterized for trafficking- related defects. These mutants will also be crossed into the tauopathy model to look specifically for alterations in severity and time of onset of pathology. These studies will assess whether or not modulation of neuronal intracellular transport can worsen or abrogate hallmark pathologies of NDs. Through in vivo imaging of transgenic and mutant Zebrafish embryos, this project will advance our understanding of debilitating neurodegenerative disease and open new avenues toward therapies that restore impaired trafficking in neurons.